while loop not using correct variable for output

Question

I have created this loop in order to find a temperature, change in albedo and latitude ice reaches after 100 iterations of the code.

import numpy as np
import matplotlib.pyplot as plt

#define constants
L = 1280
albedo = 0.15
nIters = 100
LRange = [1200, 1600] #W/m2
Episilon = 1 #no units
Sigma = 5.67E-08 #Wm-2K-4


Ice_Lat_m = 1.5
Ice_lat_c = -322.5
Alb_m = -0.01
Alb_c = 2.8

plotType = "iterDown" #"L", "iterUp", "iterDown"

x = []
y = []
while (L > LRange[0] - 1):
    for iter in range(nIters):
        T = ((L * ( 1- albedo)) / 4) / Sigma
        T = T ** (1/4)
        albedo = Alb_m * T + Alb_c
        albedo = min(albedo, 0.65)
        albedo = max(albedo, 0.15)
        lat_ice = Ice_Lat_m * T + Ice_lat_c
        lat_ice = min(lat_ice, 90)
        lat_ice = max(lat_ice, 0)
        if plotType is "iter" or plotType is "iterDown":
            x.append(iter)
            y.append(T)
    if plotType is "iter" or plotType is "iterDown":
        x.append(np.nan)
        y.append(np.nan)
    if plotType is "L":
        x.append(L)
        y.append(T)
    L = L - 10

while (L < LRange[1] + 1):
    for iter in range(nIters):
        T = ((L * ( 1- albedo)) / 4) / Sigma
        T = T ** (1/4)
        albedo = Alb_m * T + Alb_c
        albedo = min(albedo, 0.65)
        albedo = max(albedo, 0.15)
        lat_ice = Ice_Lat_m * T + Ice_lat_c
        lat_ice = min(lat_ice, 90)
        lat_ice = max(lat_ice, 0)
        if plotType is "iter" or plotType is "iterDown":
            x.append(iter)
            y.append(T)
    if plotType is "iter" or plotType is "iterDown":
        x.append(np.nan)
        y.append(np.nan)
    if plotType is "L":
        x.append(L)
        y.append(T)
    L = L + 10    

plt.plot(x, y)
plt.show()
print(T, albedo, lat_ice)

The output from this code is:

278.2748546226214 0.15 90

This tells me that the code is using the variable "LRange[1]" as the input into the loop rather than the variable "L" when it is within the range defined "LRange".

Desired output should be:

255.45242794389384 0.24547572056106137

Could anyone explain to me why this is happening? It would be greatly appreciated!

Johannes Overmann · Accepted Answer · 2021-03-10 10:23:03Z

1

You have two loops there: The first loop will count L down from 1280 to 1200, and for the second loop it will thus start with 1200.

You probably want to reset L before the second loop.

answered Mar 10, 2021 at 10:23

Johannes Overmann

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2 Comments

Ellie Nelson Over a year ago

Hi, thanks for responding. Having played around with this a bit more I have realised that both loops are using the variable LRange[0] rather L in the loop rather than L variable that has been defined. Do you know why that would be?

Johannes Overmann Over a year ago

It is hard to infer what your code tries to do. Can you please explain what your code tries to do (in terms of L and LRange[])?

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